The present invention relates to the field of immunology, specifically HIV Vaccine Technology, and, in particular, is concerned with expressing the extracellular fragment of the envelope gene, gp140, of a primary human immunodeficiency virus type 1 (HIV-1) isolate.
Acquired immunodeficiency syndrome (AIDS) is a disease which is the ultimate result of infection with human immunodeficiency virus (HIV). Currently, there is no effective vaccine which can protect the human population from HIV infection and hence the development of an efficacious HIV-vaccine and protocol for administering the same is urgently required. Previously, HIV-1 particles exhaustively inactivated by chemical treatments, a vaccinia vector encoding the whole envelope gene (gp140) of HIV-1, and purified recombinant gp120 have been evaluated as candidate HIV vaccines. Although inactivated HIV-1 virus preparations elicited a T-cell-mediated Delayed-Type Hypersensitivity (DTH) reaction in humans, and vaccinia/gp160 and gp120 recombinant vaccine candidates induced virus neutralizing antibodies, non of these immunogens have been shown to be efficacious human HIV vaccines (ref. 1, throughout this specification, various references are referred to in parenthesis to more fully describe the state of the art to which this invention pertains. Full bibliographic information for each citation is found at the end of the specification, immediately following the claims. The disclosures of these references are hereby incorporated by reference into the present disclosure). The inventors"" interest in HIV vaccinology is to develop immunogenic and cost-effective HIV-1 DNA vaccines and consider that their use alone or in conjunction with other forms of HIV-1 vaccine candidates will lead to the elicitation of more effective immune responses against HIV-1.
There has previously been described in granted European Patent No. 470,980 and U.S. Pat. No. 5,639,854, assigned to the assignee hereof, the disclosures of which are incorporated herein by reference, inter alia, the identification and characterization of a T-cell epitope of the core protein, p24E, of HIV-1. There has further been described in granted U.S. Pat. Nos. 5,759,769 and 5,795,955, assigned to the assignee hereof, and disclosures of which are incorporated by reference, the use of the T-cell epitope in the construction of immunogenic synthetic HIV-1 chimeric peptides comprising p24E linked to amino acid sequences of different B-cell epitopes of an envelope or core protein of HIV-1.
The present effort has turned to design and construct HIV DNA-based immunogens capable of eliciting cell-mediated immunity (CMI). In this context, the inventors have focused interest on the extracellular envelope fragment, gp140, expressed in a primary HIV-1 isolate, HIV-1 (BX08), for the reason that this protein is rich in motifs restricted to both the murine and human Major Histocompatibility Complex (MHC) class 1 alleles. Upon immunization with an appropriately constructed immunogen expressing the gp140 protein leads to the generation of peptides with class 1 binding capability to allow the induction of HIV-1-specific CTLs capable of killing virus infected cells to limit infection.
The invention described by the inventors is that they have found a plasmid designated, pCMV.gp140.BX08, expressing the gp140 gene under the control of a CMV promotor was immunogenic in BALB/c mice in the elicitation of CTL response directed against multiple epitopes of the gp140 protein that are restricted to different H-2d class 1 gene products.
Accordingly, in one aspect of the present invention, there is provided a vector, comprising a gene encoding the extracellular fragments of gp140 of a primary HIV-1 isolate, preferably BX08, under the control of a promotor for expression of the gene product in a host organism, thereby eliciting a cytotoxic T-cell response.
The promotor thereby is the cytomegalovirus promotor. The vector is preferably one having the identifying characteristics of plasmid pCMV.gp140.BX08, as shown in FIG. 1.
The invention further includes an immunogenic composition containing the vector as well as a method of generating a cytotoxic T-cell response in a host by administering to the host the immunogenic composition provided herein. Such immunogenic composition may be formulated for intramuscular immunization with a suitable carrier or may be formulated for gene gun delivery with gold particles.